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峨眉山玄武岩之上宣威组中的沉积型铜矿,矿石矿物以铜硫化物和自然铜为主,矿石构造大多具有结核状,前人根据此特征将其命名为“马豆子式”铜矿.本文对该矿床中的铜结核进行了矿物学和同位素方面研究.矿物学研究表明,铜结核由含铁非晶质矿物、粘土以及碳质碎屑共同胶结铜的硫化物而组成,并以交代作用和沉积作用的方式形成;结核的原始形态是凝胶状物质组合体.同位素分析显示,碳沥青的■13CPDB值在-24.8‰～-23.9‰之间,表明碳沥青是原地植物沉积变质的产物;辉铜矿的■34SV-CDT值为7.6‰～13.1‰,与二叠纪海水的■34S(约11‰)接近,斑铜矿、黄铜矿的■34SV-CDT值为21.6‰～22.2‰,和海相硫酸盐的硫同位素组成(20‰)类似,显示硫的来源不同.以上特征表明铜结核的形成过程是,含铜玄武岩经风化淋滤,铜质迁移到水体中后被粘土、含铁非晶质矿物和植物碎屑吸附,并成凝胶团悬浮与搬运,在湖泊或沼泽环境下与沉积物同生沉积成核;后期再经变质交代和热液叠加,斑铜矿交代辉铜矿、黄铜矿又叠加于斑铜矿之上,最终形成了“马豆子式”结核铜矿.
Emeishan basalts above the Xuanwei group depositional copper ore, ore minerals copper sulphide and natural copper-based, most of the ore structure with tuberculosis, according to the characteristics of its predecessors will be named This paper studies the mineralogy and isotope studies of copper nodules in this deposit, and mineralogical studies show that copper nodules consist of iron-containing amorphous minerals, clays, and carbonaceous clasts that collectively bind copper sulfides The formation of nodules was a combination of gelatinous substances.The isotopic analysis showed that the 13CPDB value of carbon pitch was between -24.8 ‰ and -23.9 ‰, indicating that carbon bitumen was a native plant The 34SV-CDT value of chalcocite is 7.6 ‰ ~ 13.1 ‰, which is close to the 34S (about 11 ‰) of Permian seawater. The 34SV-CDT values of beryllitite and chalcopyrite are 21.6 ‰ ~22.2 ‰, which is similar to the sulfur isotope composition of marine sulfate (20 ‰), showing different sources of sulfur.The above characteristics indicate that the formation of copper nodules is that the copper-bearing basalts are leached by weathering and the copper migrates to the water body After the clay, iron-containing amorphous minerals and plant debris adsorption, And become gel suspension suspension and handling, sediment nucleation and deposition in the lake or marsh environment; late metamorphic metasomatism and hydrothermal superposition, burial account for chalcocite chalcopyrite, chalcopyrite also superimposed on the spot copper On top of the mine, a “horse bean-type” nodule copper mine was finally formed.